Guidance of tiltable window leaves and swivelling cabinet doors by a straight four-bar mechanism is known (compare for example DE-32 39 989 A1 or DE-27 45 934 A1). These structures make it possible to guide the leaf around imaginary geometrical axes and to raise the leaf before swivelling out of the frame in the desired manner.
Equipping four-bar mechanisms with springs in order to support the swivel motion is furthermore known from DE-32 39 989 A1.